U.S. patent number 11,326,112 [Application Number 17/143,279] was granted by the patent office on 2022-05-10 for integrated hydrocracking/adsorption and aromatic recovery complex to utilize the aromatic bottoms stream.
This patent grant is currently assigned to Saudi Arabian Oil Company. The grantee listed for this patent is Saudi Arabian Oil Company. Invention is credited to Ali Alzaid, Omer Refa Koseoglu.
United States Patent |
11,326,112 |
Koseoglu , et al. |
May 10, 2022 |
Integrated hydrocracking/adsorption and aromatic recovery complex
to utilize the aromatic bottoms stream
Abstract
In accordance with one or more embodiments of the present
disclosure, a process for treating a hydrocarbon feedstream having
nitrogen-containing compounds and polynuclear aromatic compounds
includes contacting the hydrocarbon feedstream with an adsorbent
material; introducing the adsorbent-treated hydrocarbon feedstream
to a hydrocracking reaction unit to produce a hydrocracked effluent
stream; introducing a naphtha stream to a catalytic reforming unit
to produce a reformate stream; introducing the reformate stream to
an aromatic recovery complex to produce a light reformate stream, a
BTX stream, and an aromatic bottoms stream; and introducing the
aromatic bottoms stream to the used adsorbent to release at least a
portion of the nitrogen-containing compounds and polynuclear
compounds.
Inventors: |
Koseoglu; Omer Refa (Dhahran,
SA), Alzaid; Ali (Dammam, SA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
N/A |
SA |
|
|
Assignee: |
Saudi Arabian Oil Company
(Dhahran, SA)
|
Family
ID: |
1000005389118 |
Appl.
No.: |
17/143,279 |
Filed: |
January 7, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D
15/203 (20130101); C10G 69/10 (20130101); B01D
15/424 (20130101); B01J 20/28019 (20130101); B01J
20/12 (20130101); C10G 2300/202 (20130101); C10G
2400/30 (20130101) |
Current International
Class: |
C10G
69/10 (20060101); B01J 20/12 (20060101); B01J
20/28 (20060101); B01D 15/20 (20060101); B01D
15/42 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
International Search Report and Written Opinion dated Feb. 18, 2022
pertaining to International application No. PCT/US2021/059912 filed
Nov. 18, 2021, 14 pages. cited by applicant.
|
Primary Examiner: Nguyen; Tam M
Attorney, Agent or Firm: Dinsmore & Shohl LLP
Claims
What is claimed is:
1. A process for treating a hydrocarbon feedstream, the hydrocarbon
feedstream comprising nitrogen-containing compounds and polynuclear
aromatic compounds, the process comprising: (i) contacting the
hydrocarbon feedstream with an adsorbent material to produce an
adsorbent having an increased content of nitrogen-containing
compounds and polynuclear compounds and an adsorbent-treated
hydrocarbon feedstream having a decreased content of
nitrogen-containing compounds and polynuclear aromatic compounds;
(ii) introducing the adsorbent-treated hydrocarbon feedstream to a
hydrocracking reaction unit to produce a hydrocracked effluent
stream; (iii) introducing a naphtha stream to a catalytic reforming
unit to produce a reformate stream; (iv) introducing the reformate
stream to an aromatic recovery complex to produce a light reformate
stream, a benzene-toluene-xylene (BTX) stream, and an aromatic
bottoms stream; and (v) introducing the aromatic bottoms stream to
the adsorbent having an increased content of nitrogen-containing
compounds and polynuclear compounds to produce an adsorbent having
a decreased content of nitrogen-containing compounds and
polynuclear compounds and an aromatic bottoms stream having an
increased content of nitrogen-containing compounds and polynuclear
aromatic compounds.
2. The process of claim 1, wherein the reformate stream comprises
aromatics, alkyl aromatics, naphthenes, olefins, and
iso-paraffins.
3. The process of claim 1, wherein the aromatics bottoms stream has
a Hildebrand solubility factor of at least 19 MPa.sup.1/2.
4. The process of claim 1, wherein the adsorbent material is
selected from the group consisting of attapulgus clay, alumina,
silica, titania, activated carbon, fresh solid catalyst, spent
solid catalyst, and a combination of two or more thereof.
5. The process of claim 1, wherein the hydrocarbon feedstream is
selected from the group consisting of vacuum gas oil, de-metalized
oil, de-asphalted oil, coker gas oil, cycle oils, visbroken oil,
coal liquids, bio-oils, and a combination of two or more
thereof.
6. The process of claim 1, wherein the aromatic bottoms stream
comprises at least one compound selected from the group consisting
of alkylated mono-aromatics, uncondensed bridged di-aromatics,
condensed di-aromatics, alkylated mono-aromatics, and mixtures of
two or more thereof.
7. The process of claim 1, further comprising conveying the
aromatic bottoms stream having an increased content of
nitrogen-containing compounds and polynuclear aromatic compounds to
a fuel oil pool or other process units to recover the aromatic
bottoms stream and the nitrogen-containing compounds and
polynuclear aromatic compounds.
8. The process of claim 1, wherein the polynuclear aromatic
compounds comprise heavy polynuclear aromatic compounds having
seven or more fused aromatic rings.
9. The process of claim 1, wherein the hydrocracking reaction unit
performs single-stage once through hydrocracking, series flow
hydrocracking with recycle, series flow hydrocracking without
recycle, or two stage recycle hydrocracking to produce the
hydrocracked effluent stream.
10. The process of claim 1, wherein the adsorbent material is in
the form of pellets, spheres, extrudates, or natural shapes and has
a size in the range of 4-60 mesh.
11. The process of claim 1, wherein the process does not comprise a
solvent desorption step to produce an adsorbent having a decreased
content of nitrogen-containing compounds and polynuclear compounds
and an aromatic bottoms stream having an increased content of
nitrogen-containing compounds and polynuclear aromatic
compounds.
12. The process of claim 1, further comprising: introducing the
hydrocracked effluent stream to a high pressure separation zone to
produce a degassed effluent stream; introducing the degassed
effluent stream to a fractionating zone to produce at least one
hydrocarbon fraction comprising nitrogen-containing compounds and
polynuclear compounds; and contacting the at least one hydrocarbon
fraction comprising nitrogen-containing compounds and polynuclear
compounds with an adsorbent material to produce an adsorbent having
an increased content of nitrogen-containing compounds and
polynuclear compounds and a second adsorbent-treated hydrocarbon
feedstream having a decreased content of nitrogen-containing
compounds and polynuclear aromatic compounds.
Description
FIELD
Embodiments of the present disclosure generally relate to
hydrocracking of hydrocarbon oil, and pertain particularly to a
process and system for removing polynuclear aromatic compounds from
the hydrocarbon feedstream.
TECHNICAL BACKGROUND
Hydrocracking processes are used commercially in a large number of
petroleum refineries to process a variety of hydrocarbon feeds
boiling in the range of 370.degree. C. to 565.degree. C. in
conventional hydrocracking units and boiling at 565.degree. C. and
above in residue hydrocracking units. In general, hydrocracking
processes split the molecules of the hydrocarbon feed into smaller,
i.e., lighter, molecules having higher average volatility and
economic value. Additionally, hydrocracking processes typically
improve the quality of the hydrocarbon feedstock by increasing the
hydrogen-to-carbon ratio and by removing organosulfur and organo
nitrogen compounds.
Generally undesirable byproducts of hydrocracking processes include
polynuclear aromatic compounds (PNA), having six or fewer fused
aromatic rings, and heavy polynuclear aromatic compounds (HPNA),
having seven or more fused aromatic rings. The PNA and/or HPNA may
cause fouling of refining equipment. As a result, methods of
removing PNA and/or HPNA from hydrocracking systems have been
developed, including passing a hydrocracked feedstream over an
adsorbent material that extracts the PNA and/or HPNA from the
hydrocracked feedstream. Such methods may be referred to as "PNA
and/or HPNA adsorption processes." In a PNA and/or HPNA adsorption
processes, recycling of the adsorbent material by a controlled
desorption of the PNA and/or HPNA from the adsorbent material is
desirable.
SUMMARY
Therefore, there is a continual need for systems and processes for
desorbing PNA and/or HPNA from adsorbent materials in hydrocracking
processes. Described herein are processes and systems that allow
the aromatic bottoms stream to act as a desorption agent for
desorbing PNA and/or HPNA from the adsorbent materials.
According to an embodiment, a process for treating a hydrocarbon
feedstream, the hydrocarbon feedstream comprising
nitrogen-containing compounds and polynuclear aromatic compounds,
includes: (i) contacting the hydrocarbon feedstream with an
adsorbent material to produce an adsorbent having an increased
content of nitrogen-containing compounds and polynuclear compounds
and an adsorbent-treated hydrocarbon feedstream having a decreased
content of nitrogen-containing compounds and polynuclear aromatic
compounds; (ii) introducing the adsorbent-treated hydrocarbon
feedstream to a hydrocracking reaction unit to produce a
hydrocracked effluent stream; (iii) introducing a naphtha stream to
a catalytic reforming unit to produce a reformate stream; (iv)
introducing the reformate stream to an aromatic recovery complex to
produce a light reformate stream, a benzene-toluene-xylene (BTX)
stream, and an aromatic bottoms stream; and (v) introducing the
aromatic bottoms stream to the adsorbent having an increased
content of nitrogen-containing compounds and polynuclear compounds
to produce an adsorbent having a decreased content of
nitrogen-containing compounds and polynuclear compounds and an
aromatic bottoms stream having an increased content of
nitrogen-containing compounds and polynuclear aromatic
compounds.
According to an embodiment, a system for treating a hydrocarbon
feedstream, the hydrocarbon feedstream comprising
nitrogen-containing compounds and polynuclear aromatic compounds,
including: an adsorption zone comprising an adsorbent material for
adsorbing at least a portion of the nitrogen-containing compounds
and polynuclear aromatic compounds thereby converting the
hydrocarbon feedstream into an adsorbent-treated hydrocarbon
feedstream having a decreased content of nitrogen-containing
compounds and polynuclear aromatic compounds; an aromatic recovery
complex for producing an aromatic bottoms stream, the aromatic
recovery complex having an outlet that is fluidly coupled to an
inlet of the adsorption zone; and a conduit in fluid communication
with the outlet of the aromatic recovery complex and the inlet of
the adsorption zone for conveying at least a portion of the
aromatic bottoms stream to the adsorption zone for desorbing the
nitrogen-containing compounds and polynuclear aromatic compounds
from the adsorbent materials.
Additional features and advantages of the embodiments described
herein will be set forth in the detailed description which follows,
and in part will be readily apparent to those skilled in the art
from that description or recognized by practicing the embodiments
described, including the detailed description and the claims which
are provided infra.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description of specific embodiments of the
present disclosure can be best understood when read in conjunction
with the following drawings in which:
FIG. 1 depicts a process flow diagram of an integrated
hydrocracking apparatus in accordance with embodiments described
herein;
FIG. 2 depicts a process flow diagram of an aromatic recovery
complex in accordance with embodiments described herein; and
FIG. 3 depicts a process flow diagram of an integrated
hydrocracking apparatus having two adsorption zones in accordance
with embodiments described herein.
DETAILED DESCRIPTION
As used herein, the term "hydrocarbon oil" or "hydrocarbon
feedstock" refers to an oily liquid composed mostly of a mixture of
hydrocarbon compounds. Hydrocarbon oil may include refined oil
obtained from crude oil, synthetic crude oil, bitumen, oil sand,
shale oil, or coal oil. The term "refined oil" includes, but is not
limited to, vacuum gas oil (VGO), deasphalted oil (DAO) obtained
from a solvent deasphalting process, demetallized oil (DMO), light
and/or heavy coker gas oil obtained from a coker process, cycle oil
obtained from a fluid catalytic cracking (FCC) process, and gas oil
obtained from a visbreaking process.
As used herein, the term "hydrocarbon" refers to a chemical
compound composed entirely of carbon and hydrogen atoms. An
expression such as "C.sub.x-C.sub.y hydrocarbon" refers to a
hydrocarbon having from x to y carbon atoms. For instance, a
C.sub.1-C.sub.5 hydrocarbon includes methane, ethane, propane, the
butanes, and the pentanes.
As used herein, the term "hydrogen/oil ratio" or "hydrogen-to-oil
ratio" refers to a standard measure of the volume rate of hydrogen
circulating through the reactor with respect to the volume of feed.
The hydrogen/oil ratio may be determined by comparing the flow
volume of the hydrogen gas stream and the flow volume of the
hydrocarbon feed.
As used herein, the term "liquid hourly space velocity" or "LHSV"
refers to the ratio of the liquid flow rate of the hydrocarbon feed
to the catalyst volume or mass.
As used herein, the term "conduit" includes casings, liners, pipes,
tubes, coiled tubing, and mechanical structures with interior
voids.
As used herein, the term "decreased content" of a substance means
that a concentration of the substance is greater before passing
through a stage of the process under examination than it is after
passing through the stage. As used herein, the term "increased
content" of a substance means that a concentration of the substance
is greater after passing through a stage of the process under
examination than it is before passing through the stage.
The overall Hildebrand solubility parameter, which has been
calculated for numerous compounds, is a well-known measure of
polarity and is believed to be derived from the cohesive energy
density of the solvent, which in turn is derived from the heat of
vaporization. See Joel H. Hildebrand, Journal of Paint Technology,
Vol. 39, No. 505, February 1967. Without intending to be bound by
any particular theory, it is believed that when a liquid is heated
to its boiling point, energy is added to the liquid, resulting in
an increase in the temperature of the liquid. Once the liquid
reaches its boiling point, however, the further addition of heat
does not cause a further increase in temperature. The energy that
is added is entirely used to separate the molecules of the liquid
and boil them away into a gas. If the amount of energy (in
calories) added from the onset of boiling to the point when all the
liquid has boiled away is measured, the measurement will provide a
direct indication of the amount of energy required to separate the
liquid into a gas, and thus the amount of van der Waals forces that
held the molecules of the liquid together. A liquid with a low
boiling point may require considerable energy to vaporize, while a
liquid with a higher boiling point may vaporize quite readily, or
vice versa. The energy required to vaporize the liquid is called
the heat of vaporization. From the heat of vaporization, in
calories per cubic centimeter of liquid, the cohesive energy
density of the liquid may be calculated as follows:
.DELTA..times. ##EQU00001## where c is the cohesive energy density
in MPa; .DELTA.H is the heat of vaporization; R is the gas
constant; T is the temperature; and V.sub.m is the molar volume.
The Hildebrand solubility factor, .delta., is the square root of
the cohesive energy density. The Hildebrand solubility factors are
known for several solvents. However, such Hildebrand solubility
factors were not readily available for the aromatic bottoms stream,
which have now been calculated and reported herein. Table 1
provides known Hildebrand solubility factors for conventional
solvents, heptane, n-dodecane, and benzene, and such factors
calculated for kerosene, light gas oil, and two varieties of
aromatic bottoms. It is believed that the aromatics bottom stream
may have a Hildebrand solubility factor of at least 19 MPa.sup.1/2,
such as from 19 MPa.sup.1/2 to 22 MPa.sup.1/2.
TABLE-US-00001 TABLE 1 Hildebrand Solubility Factors for Various
Solvents and Refining Products Solvent .DELTA. (MPa.sup.1/2)
Heptane 15.3 n-Dodecane 16.0 Benzene 18.7 Kerosene 16.3 Light gas
oil 15.7 Aromatic Bottoms (full range) 20.7 Aromatic Bottoms
(.gtoreq.180.degree. C. fraction) 21.2
Referring now to FIG. 1, a process flow diagram of an integrated
hydrocracking apparatus 100 including feed/bottoms treatment is
provided. Apparatus 100 includes an adsorption zone 110, a
hydrocracking reaction zone 130 containing hydrocracking catalysts,
an optional high-pressure separation zone 150, a fractionating zone
160, a catalytic reforming unit 170, and an aromatic recovery
complex 180.
Adsorption zone 110 includes an inlet 114 in fluid communication
with a source of a first heavy hydrocarbon feedstream via a conduit
102, and hydrocracking reaction product fractionator bottoms via a
conduit 164, which is in fluid communication with an
unconverted/partially converted fractionator bottoms outlet 162 of
fractionating zone 160. In addition, adsorption zone 110 includes a
cleaned feedstream outlet 116 in fluid communication with an inlet
136 of hydrocracking reaction zone 130 via a conduit 120.
Feed inlet 136 of hydrocracking zone 130 may also be in fluid
communication with an optional source of a second heavy hydrocarbon
feedstream via a conduit 132. In addition, inlet 136 is in fluid
communication with a source of hydrogen via a conduit 134 and
optionally a hydrogen recycle stream from outlet 154 of
high-pressure separation zone 150 via a conduit 156 for recovering
excess hydrogen. An outlet 138 of hydrocracking reaction zone 130
may be in fluid communication with an inlet 140 of high-pressure
separation zone 150. In embodiments in which there is not an excess
of hydrogen to be recovered, i.e., stoichiometric or
near-stoichiometric hydrogen feed is provided, high pressure
separation zone 150 can be bypassed or eliminated, and outlet 138
of hydrocracking reaction zone 130 may be in fluid communication
with inlet 158 of the fractionating zone 160. However, in addition
to excess hydrogen, high pressure separation zone 150 may also be
used to remove other gases, such as hydrogen sulfide and C.sub.1 to
C.sub.4 gases.
High-pressure separation zone 150 includes an outlet 152 in fluid
communication with an inlet 158 of the fractionating zone 160 for
conveying cracked, partially cracked and unconverted hydrocarbons,
and an outlet 154 in fluid communication with inlet 136 of the
hydrocracking reaction zone 130 for conveying recycle hydrogen.
Fractionating zone 160 further includes outlet 162 in fluid
communication with inlet 114 of adsorption zone 110 and a bleed
outlet 163, and an outlet 166 to discharge cracked product. In
embodiments, fractionating zone 160 splits the hydrocracker
products into several fractions. For instance, fractionating zone
160 may split the hydrocracker products into light naphtha
(products from the initial boiling point to 75.degree. C.), heavy
naphtha (boiling from 75.degree. C. to 180.degree. C.), kerosene
(boiling from 180.degree. C. to 250.degree.), diesel (boiling from
250.degree. C. to 375.degree. C.), and unconverted oil (boiling at
375.degree. C. and above).
Aromatic bottoms used for desorption are prepared as follows.
Naphtha feed is in fluid communication with inlet 172 of catalytic
reforming unit 170 through conduit 168. The product of the
reforming unit 170, the reformate, is in fluid communication with
outlet 174 of catalytic reforming unit 170 and inlet 176 of
aromatic recovery complex 180 through conduit 178. In embodiments,
the reformate stream includes aromatics, alkyl aromatics,
naphthenes, olefins, and iso-paraffins. Aromatic recovery complex
180 separates the reformate into benzene, toluene, xylene,
non-aromatic raffinate, and aromatic bottoms. Referring to FIG. 2,
in a typical refinery with an aromatic recovery complex 180, the
reformate from catalytic reforming unit 170 is processed in an
aromatic recovery complex 180 to recover high value aromatics,
i.e., benzene, toluene, and xylenes (commonly called BTX). The
reformate from the catalytic reforming unit 170 is split into two
fractions: light reformate and heavy reformate or BTX stream. As
used herein, the term "light reformate" refers to a fraction of the
reformate with a carbon number C.sub.5-C.sub.6. As used herein, the
term "heavy reformate" refers to a fraction of the reformate with a
carbon number C.sub.7 or higher. The light reformate stream is sent
to a benzene extraction unit 1120 through conduit 182 to extract
the benzene and recover gasoline that is substantially free of
benzene. As used in this context, "substantially free of benzene"
means that the gasoline contains 1% by volume (vol. %) or less of
the benzene, or 0.75 vol. % or less of the benzene, or 0.5 vol. %
or less of the benzene, or 0.25 vol. % or less of the benzene, or
100 parts per million by volume (ppmv) or less of the benzene, or
75 ppmv or less of the benzene, or 50 ppmv or less of the benzene,
or 25 ppmv or less of the benzene. The heavy reformate stream
optionally may be split into a C.sub.7 stream and a C.sub.8 and
higher stream. The C.sub.7 stream may be used as a gasoline
blending composition or directed to a transalkylation unit, as
described in U.S. Pre-Grant Publication No. 2020/0062675, the
entire content of which is incorporated herein by reference. The
C.sub.8 and higher stream may be deolefinated and sent to a
p-xylene extraction unit 1140 through conduit 178 to recover
p-xylene, which exits p-xylene extraction unit 1140 through conduit
193. Other xylenes are recovered and sent to a xylene isomerization
unit 1160 through conduit 191 to convert them to p-xylene. The
converted fraction is recycled back to the p-xylene extraction unit
1140 via conduit 184. The heavy fraction stream 192 from the
p-xylene extraction unit 1140 is recovered as process reject or
bottoms, including aromatic bottoms.
Without intending to be bound by any particular theory, it is
believed that the aromatic bottoms form as follows. Because olefins
are detrimental in the extraction and adsorption process within an
aromatic recovery complex, they are usually removed using a clay
tower or by selective hydrogenation. Due to the acidic nature of
the clays, olefinic aromatics, such as styrene, react with another
aromatic molecule via an alkylation reaction to form bridged
di-aromatic molecules. After the separation of C.sub.6 to C.sub.8
aromatics, these di-aromatic molecules remain in the process reject
or bottoms stream of the aromatic complex, which stream is a low
quality stream and may be used to obtain gasoline blending
components. The aromatic bottoms stream has a high Hildebrand
solubility factor and can be used to dissipate the PNA compounds in
the hydrocracking reactor outlets, thus minimizing or eliminating
deposition of such molecules downstream of the reactor, usually at
the heat exchangers.
An exemplary aromatic bottoms stream has a density of 0.9819 g/ml,
and in some embodiments, the components of the aromatic bottoms
stream may have an initial boiling point of less than or equal to
198.degree. C., a T10 true boiling point (TBP), referring to when
at least 10% of the aromatic bottoms fraction has evaporated, of
less than or equal to 211.degree. C., a T30 TBP of less than or
equal to 236.degree. C., a T50 TBP of less than or equal to
274.degree. C., a T70 TBP of less than or equal to 302.degree. C.,
a T90 TBP of less than or equal to 329.degree. C., and a final
boiling point of less than or equal to 400.degree. C. An analysis
of an exemplary aromatic bottoms stream provides the composition
shown in Table 1. In embodiments, the aromatic bottoms stream
comprises at least one compound selected from the group consisting
of alkylated mono-aromatics, uncondensed bridged di-aromatics,
condensed di-aromatics, alkylated mono-aromatics, and mixtures of
two or more thereof.
TABLE-US-00002 TABLE 1 Components of an exemplary aromatic bottoms
stream Component Amount (wt. %) Paraffins 0.1 Mono-naphthenes 0.1
Di-naphthenes 0.1 Mono-aromatics 10.75 Naphtheno-mono-aromatics
12.1 Di-aromatics 65.8 Naphtheno-di-aromatics 6.9
Tri/tetra-aromatics 4.3 BTX 0.1
Referring again to FIG. 1, the BTX stream is in fluid communication
with outlet 184 of aromatic recovery complex 180 through conduit
186, to be collected for further processing. The aromatic bottoms
stream is in fluid communication with outlet 188 of aromatic
recovery complex 180 and inlet 114 of adsorption zone 110 through
conduit 192.
In operation of the system 100, a combined stream including a first
heavy hydrocarbon feedstream via conduit 102 and a hydrocracking
reaction bottoms stream via conduit 164, and optionally solvent via
conduit 104 from fractionating zone 160 or from another source, are
introduced into the adsorption zone 110 via inlet 114. Solvent can
be optionally used to facilitate elution of the feedstock mixture
over the adsorbent. The concentrations of nitrogen-containing
compounds, sulfur-containing compounds, and HPNA compounds present
in the hydrocarbon feedstream are reduced in the adsorption zone
110 by contact with adsorbent 112. The HPNA compounds may include 7
or more, 8 or more, 9 or more, or even 10 or more fused aromatic
rings.
An adsorbent-treated hydrocracking feedstream is discharged from
adsorption zone 110 via outlet 116 and conveyed to inlet 136 of
hydrocracking reaction zone 130 via and conduit 120, along with the
second hydrocarbon feedstream which optionally may be introduced
into inlet 136 of hydrocracking reaction zone 130 via conduit 132.
In embodiments in which elution solvent is utilized, it is
distilled and recovered in fractionator 118.
An effective quantity of hydrogen for hydrocracking reactions is
provided via conduits 134 and optionally recycle hydrogen conduit
156. Hydrocracking reaction effluents are discharged from outlet
138 of hydrocracking reaction zone 130. The hydrocracking reaction
effluents are conveyed to inlet 140 of high-pressure separation
zone 150. A gas stream, which mainly contains hydrogen, but may
also contain other gases such as C.sub.1 to C.sub.4 hydrocarbons,
H.sub.2S, and NH.sub.3, is separated from the converted, partially
converted and unconverted hydrocarbons in the high-pressure
separation zone 150, and is discharged via outlet 154 and recycled
to hydrocracking reaction zone 130 via conduit 156. Converted,
partially converted, and unconverted hydrocarbons, which includes
HPNA compounds formed in the hydrocracking reaction zone 130, are
discharged via outlet 152 to inlet 158 of fractionating zone 160. A
cracked product stream is discharged via outlet 166 and can be
further processed and/or blended in downstream refinery operations
to produce gasoline, kerosene and/or diesel fuel. At least a
portion of the fractionator bottoms from the hydrocracking reaction
effluent, including HPNA compounds formed in the hydrocracking
reaction zone 130, are discharged from outlet 162 and are recycled
to adsorption zone 110 via conduit 164. A portion of the
fractionator bottoms from the hydrocracking reaction effluent is
removed from bleed outlet 163 to remove a portion of the HPNA
compounds, which could cause equipment fouling. The concentration
of HPNA compounds in the hydrocracking effluent fractionator
bottoms is reduced in adsorption zone 110. For instance, the
concentration of HPNA compounds prior to passing through the
adsorption zone 110 may be from 10 parts per million by weight
(ppmw) to 10000 ppmw, from 10 ppmw to 9000 ppmw, from 10 ppmw to
8000 ppmw, from 10 ppmw to 7000 ppmw, from 10 ppmw to 6000 ppmw,
from 10 ppmw to 5000 ppmw, from 10 ppmw to 4000 ppmw, from 10 ppmw
to 3000 ppmw, from 10 ppmw to 2000 ppmw, from 10 ppmw to 1000 ppmw,
from 10 ppmw to 900 ppmw, from 10 ppmw to 800 ppmw, from 10 ppmw to
700 ppmw, from 10 ppmw to 600 ppmw, from 10 ppmw to 500 ppmw, from
10 ppmw to 400 ppmw, from 10 ppmw to 300 ppmw, from 10 ppmw to 200
ppmw, from 10 ppmw to 100 ppmw, from 100 ppmw to 10000 ppmw, from
200 ppmw to 10000 ppmw, from 300 ppmw to 10000 ppmw, from 400 ppmw
to 10000 ppmw, from 500 ppmw to 10000 ppmw, from 600 ppmw to 10000
ppmw, from 700 ppmw to 10000 ppmw, from 800 ppmw to 10000 ppmw,
from 900 ppmw to 10000 ppmw, from 1000 ppmw to 10000 ppmw, from
2000 ppmw to 10000 ppmw, from 3000 ppmw to 10000 ppmw, from 4000
ppmw to 10000 ppmw, from 5000 ppmw to 10000 ppmw, from 6000 ppmw to
10000 ppmw, from 7000 ppmw to 10000 ppmw, from 8000 ppmw to 10000
ppmw, or even from 9000 ppmw to 10000 ppmw. Further, the
concentration of HPNA adsorbent-treated hydrocarbon feedstream may
be from 0 ppmw to 500 ppmw, from 0 ppmw to 450 ppmw, from 0 ppmw to
400 ppmw, from 0 ppmw to 350 ppmw, from 0 ppmw to 300 ppmw, from 0
ppmw to 250 ppmw, from 0 ppmw to 200 ppmw, from 0 ppmw to 150 ppmw,
from 0 ppmw to 100 ppmw, from 0 ppmw to 90 ppmw, from 0 ppmw to 80
ppmw, from 0 ppmw to 70 ppmw, from 0 ppmw to 60 ppmw, from 0 ppmw
to 50 ppmw, from 0 ppmw to 40 ppmw, from 0 ppmw to 30 ppmw, from 0
ppmw to 20 ppmw, from 0 ppmw to 10 ppmw, from 10 ppmw to 500 ppmw,
from 20 ppmw to 500 ppmw, from 30 ppmw to 500 ppmw, from 40 ppmw to
500 ppmw, from 50 ppmw to 500 ppmw, from 60 ppmw to 500 ppmw, from
70 ppmw to 500 ppmw, from 80 ppmw to 500 ppmw, from 90 ppmw to 500
ppmw, from 100 ppmw to 500 ppmw, from 150 ppmw to 500 ppmw, from
200 ppmw to 500 ppmw, from 250 ppmw to 500 ppmw, from 300 ppmw to
500 ppmw, from 350 ppmw to 500 ppmw, from 400 ppmw to 500 ppmw, or
even from 450 ppmw to 500 ppmw. In particular, in system 100, both
the hydrocracking reaction fractionator bottoms and the first heavy
hydrocarbon feedstream are combined and contacted with adsorbent
material 112 in adsorption zone 110. The adsorbent-treated
hydrocracking feed may optionally be combined with the second heavy
hydrocarbon feedstream for cracking in the hydrocracking reaction
zone 130.
In certain embodiments, the adsorption zone includes columns that
are operated in swing mode so that production of the cleaned
feedstock is continuous. When the adsorbent material 112 in column
110 a or 110 b becomes saturated with adsorbed nitrogen-containing
compounds, sulfur-containing compounds, and/or HPNA compounds, the
flow of the combined feedstream is directed to the other column.
The adsorbed compounds are desorbed by the aromatic bottoms stream
produced by catalytic reforming unit 170 and aromatic recovery
complex 180. In embodiments, the aromatics bottom stream may have a
Hildebrand solubility factor of at least 19 MPa.sup.1/2, such as
from 19 MPa.sup.1/2 to 22 MPa.sup.1/2. An aromatic bottoms stream
having an increased content of nitrogen-containing compounds and
PNA compounds is thereby provided, which may then be conveyed to a
fuel oil pool or other process units to separate adsorbed species
from the aromatic bottoms solvent.
In embodiments, the desorption step is not performed by solvent
desorption or heat desorption. Solvent desorption is typically
performed using polar solvents or non-polar solvents. The non-polar
solvents typically have an overall Hildebrand solubility parameter
of less than or equal to 16 MPa.sup.1/2. Suitable non-polar
solvents include, e.g., saturated aliphatic hydrocarbons such as
pentanes, hexanes, heptanes, paraffinic naphtha, C.sub.5-C.sub.11,
kerosene C.sub.12-C.sub.15, diesel C.sub.16-C.sub.20, normal and
branched paraffins, and mixtures or any of these solvents. Polar
solvents typically have a Hildebrand solubility parameter greater
than or equal to about 16.5 MPa.sup.1/2 and include (with the
Hildebrand solubility factor given in parentheses) toluene (18.31
MPa.sup.1/2), benzene (18.7 MPa.sup.1/2), xylenes (18.25
MPa.sup.1/2), and tetrahydrofuran (18.5 MPa.sup.1/2).
Referring to FIG. 3, a process flow diagram of an integrated
hydrocracking apparatus 200 including feed pretreatment and bottoms
treatment is provided. Apparatus 200 includes a first adsorption
zone 210, a hydrocracking reaction zone 230 containing
hydrocracking catalysts, a high-pressure separation zone 250, a
fractionating zone 260, a catalytic reforming unit 270, an aromatic
recovery complex 280, and a second adsorption zone 290.
First adsorption zone 210 includes an inlet 214 in fluid
communication with a source of first heavy hydrocarbon feedstream
via a conduit 202 (and optionally a source of solvent as described
with respect to FIG. 1, not shown in FIG. 3), and a cleaned
feedstream outlet 216 in fluid communication with an inlet 236 of
hydrocracking reaction zone 230 via a conduit 217.
Feed inlet 236 of hydrocracking reaction zone 230 optionally may
also be in fluid communication with a source of second hydrocarbon
feedstream via a conduit 232. In addition, inlet 236 is in fluid
communication with a source of hydrogen via a conduit 234 and
hydrogen recycle stream from outlet 254 of high-pressure separation
zone 250 via a conduit 256. As noted with respect to the discussion
of apparatus 100 in FIG. 1, the high pressure separation zone can
be bypassed or eliminated, for instance, if there is little or no
excess hydrogen. However, in addition to excess hydrogen, high
pressure separation zone 250 may also be used to remove other
gases, such as hydrogen sulfide and C.sub.1 to C.sub.4 gases.
Hydrocracking reaction zone 230 includes an outlet 238 in fluid
communication with an inlet 240 of high-pressure separation zone
250.
High-pressure separation zone 250 also includes an outlet 252 in
fluid communication with an inlet 258 of fractionating zone 260 for
conveying cracked, partially cracked and unconverted hydrocarbons,
and an outlet 254 in fluid communication with the hydrocracking
reaction zone 230 for conveying recycle hydrogen. Fractionating
zone 260 further includes outlet 262 in fluid communication with
inlet 292 of second adsorption zone 290, and an outlet 264 to
discharge cracked product. In embodiments, fractionating zone 260
splits the hydrocracker products into several fractions. For
instance, fractionating zone 260 may split the hydrocracker
products into light naphtha (products from the initial boiling
point to 75.degree. C.), heavy naphtha (boiling from 75.degree. C.
to 180.degree. C.), kerosene (boiling from 180.degree. C. to
250.degree.), diesel (boiling from 250.degree. C. to 375.degree.
C.), and unconverted oil (boiling at 375.degree. C. and above).
Second adsorption zone 290 includes inlet 292 in fluid
communication with fractionating zone outlet 262 (and optionally a
source of solvent as described with respect to FIG. 1, not shown in
FIG. 3), and an outlet 294 in fluid communication with inlet 236 of
hydrocracking reaction zone 230 via a conduit 296.
Aromatic bottoms used for desorption are prepared as follows.
Naphtha feed is in fluid communication with inlet 172 of catalytic
reforming unit 270 through conduit 168. The reformate is in fluid
communication with outlet 174 of catalytic reforming unit 270 and
inlet 176 of aromatic recovery complex 280 through conduit 178.
Aromatic recovery complex 280 separates the reformate into benzene,
toluene, xylene, and aromatic bottoms. The benzene, toluene, and
xylene (together "BTX") are in fluid communication with outlet 184
of aromatic recovery complex 280 through conduit 186, to be
collected for further processing. The aromatic bottoms stream is in
fluid communication with outlet 188 of aromatic recovery complex
180 and inlet 214 of first adsorption zone 210 through conduit 192
and/or inlet 292 of second adsorption zone 290.
In operation of the system 200, a first heavy hydrocarbon
feedstream is conveyed via conduit 202 to inlet 214 of first
adsorption zone 210. The concentrations of nitrogen-containing
compounds, sulfur-containing compounds and HPNA compounds in the
first heavy hydrocarbon feedstream are reduced in first adsorption
zone 210.
An adsorbent-treated first heavy hydrocarbon feedstream is
discharged from outlet 216 of adsorption zone 210 and conveyed to
inlet 236 of hydrocracking reaction zone 230 via conduit 217. A
second hydrocarbon feedstream is also introduced into the
hydrocracking reaction zone 230 via conduit 232. An effective
quantity of hydrogen for hydrocracking reactions is provided via
conduits 234, 256. Hydrocracked effluents are discharged via outlet
238 to inlet 240 of high-pressure separation zone 250. The
high-pressure separation zone 250 operates at a pressure similar to
that of the hydrocracking reaction zone 230. However, from 0.2 MPa
to 1 MPa of pressure may be lost in the high-pressure separation
zone 250 depending on the number of heat exchange units used in the
high-pressure separation zone 250. For example, approximately 0.06
MPa of pressure may be lost per heat exchanger used. In
embodiments, the high-pressure separation zone 250 may be operated
at a temperature from 220.degree. C. to 260.degree. C., from
230.degree. C. to 260.degree. C., from 240.degree. C. to
260.degree. C., from 250.degree. C. to 260.degree. C., from
220.degree. C. to 250.degree. C., from 220.degree. C. to
240.degree. C., or even from 220.degree. C. to 230.degree. C.
A gas stream, which primarily contains hydrogen, is separated from
the converted, partially converted and unconverted hydrocarbons in
the high-pressure separation zone 250, and is discharged via outlet
254 and recycled to hydrocracking reaction zone 230 via conduit 256
as-is or after purification to hydrogen sulfide and/or C.sub.1 to
C.sub.4 gases, when present. Converted, partially converted and
unconverted hydrocarbons, including HPNA compounds formed in the
hydrocracking reaction zone 230, are discharged via outlet 252 to
inlet 258 of fractionating zone 260. A cracked product stream is
discharged via outlet 264 and can be further processed and/or
blended in downstream refinery operations to produce gasoline,
kerosene and/or diesel fuel. Unconverted and partially cracked
fractionator bottoms, including HPNA compounds formed in the
hydrocracking reaction zone 230, are discharged from outlet 262 and
at least a portion thereof is conveyed to inlet 292 of second
adsorption zone 290, with the remainder removed via a bleed outlet
263. The concentration of HPNA compounds in the unconverted
fractionator bottoms is reduced in the second adsorption zone 290,
thereby improving the quality of the recycle stream.
Adsorbent-treated unconverted fractionator bottoms are sent to the
hydrocracking reaction zone 230 via outlet 294 in fluid
communication with inlet 236 for further cracking. The adsorbed
compounds in first adsorption zone 210 and second adsorption zone
290 are desorbed by the aromatic bottoms stream produced by
catalytic reforming unit 270 and aromatic recovery complex 280.
By employing distinct adsorption zones 210, 290, the content of the
individual feeds to these adsorption zones can be specifically
targeted. That is, nitrogen-containing compounds, sulfur-containing
compounds and HPNA compounds from the initial feed can be removed
in the first adsorption zone 210 under a first set of operating
conditions and using a first adsorbent material, and HPNA compounds
formed during the hydrocracking process can be removed in the
second adsorption zone 290 under a second set of operating
conditions and using a second adsorbent material. Further, the
first adsorption zone 210 and second adsorption zone 290 may
undergo desorption with the aromatic bottoms stream either
simultaneously or independently.
The feedstreams for use in above-described systems and processes
may be a partially refined oil product obtained from various
sources. In general, the first heavy feedstream is one or more of
VGO from a vacuum distillation operation, DMO from a solvent
demetalizing operation or DAO from a solvent deasphalting
operations, coker gas oils from coker operations, cycle oils from
fluid catalytic cracking operations, visbroken oils from
visbreaking operations. The first heavy feedstream generally has a
boiling point of from 350.degree. C. to 800.degree. C., and in
certain embodiments of from 500.degree. C. to 700.degree. C.
The second heavy hydrocarbon feedstream is generally VGO from a
vacuum distillation operation and contains hydrocarbons having a
boiling point of from 350.degree. C. to 600.degree. C., and in
certain embodiments from 350.degree. C. to 570.degree. C.
Suitable reaction apparatuses for the hydrocracking reaction zone
include fixed bed reactors, moving bed reactors, ebullated bed
reactors, baffle-equipped slurry bath reactors, stirring bath
reactors, rotary tube reactors, slurry bed reactors, or other
suitable reaction apparatuses as appreciated by one of ordinary
skill in the art. In certain embodiments, for example for VGO and
similar feedstreams, fixed bed reactors are utilized. In additional
embodiments, for example for heavier feedstreams and other
difficult to crack feedstreams, ebullated bed reactors are
utilized. In embodiments, the hydrocracker may perform single-stage
once through hydrocracking, series flow hydrocracking with recycle,
series flow hydrocracking without recycle, or two stage recycle
hydrocracking to produce the hydrocracked effluent stream.
In general, the operating conditions for the reactor of a
hydrocracking zone include: reaction temperature of 300.degree. C.
to 500.degree. C., in certain embodiments 330.degree. C. to
475.degree. C., and in further embodiments 330.degree. C. to
450.degree. C.; hydrogen partial pressure of 60 kg/cm.sup.2 to 300
kg/cm.sup.2, in certain embodiments 100 kg/cm.sup.2 to 200
kg/cm.sup.2, and in further embodiments 130 kg/cm.sup.2 to 180
kg/cm.sup.2; liquid hourly space velocity of 0.1 h.sup.-1 to 10
h.sup.-1, in certain embodiments 0.25 h.sup.-1 to 5 h.sup.-1, and
in further embodiments 0.5 h.sup.-1 to 2 h.sup.-1; hydrogen/oil
ratio of 500 normalized m.sup.3 per m.sup.3 (Nm.sup.3/m.sup.3) to
2500 Nm.sup.3/m.sup.3, in certain embodiments 800 Nm.sup.3/m.sup.3
to 2000 Nm.sup.3/m.sup.3, and in further embodiments 1000
Nm.sup.3/m.sup.3 to 1500 Nm.sup.3/m.sup.3.
In certain embodiments, the hydrocracking catalyst includes any one
of or combination including amorphous alumina catalysts, amorphous
silica alumina catalysts, titania catalysts, natural or synthetic
zeolite based catalyst, or a combination thereof. The hydrocracking
catalyst can possess an active phase material including, in certain
embodiments, any one of or combination including Ni, W, Mo, or Co.
In certain embodiments in which an objective is
hydrodenitrogenation, acidic alumina or silica-alumina or titania
based catalysts loaded with Ni--Mo or Ni--W active metals, or
combinations thereof, are used. In embodiments in which the
objective is to remove all nitrogen and to increase the conversion
of hydrocarbons, silica-alumina, zeolite, or combination thereof
are used as catalysts, with active metals including Ni--Mo, Ni--W
or combinations thereof.
In embodiments, the catalytic reforming unit may be operated at a
temperature from 260.degree. C. to 560.degree. C., from 270.degree.
C. to 560.degree. C., from 280.degree. C. to 560.degree. C., from
290.degree. C. to 560.degree. C., from 300.degree. C. to
560.degree. C., from 310.degree. C. to 560.degree. C., from
320.degree. C. to 560.degree. C., from 330.degree. C. to
560.degree. C., from 340.degree. C. to 560.degree. C., from
350.degree. C. to 560.degree. C., from 360.degree. C. to
560.degree. C., from 370.degree. C. to 560.degree. C., from
380.degree. C. to 560.degree. C., from 390.degree. C. to
560.degree. C., from 400.degree. C. to 560.degree. C., from
410.degree. C. to 560.degree. C., from 420.degree. C. to
560.degree. C., from 430.degree. C. to 560.degree. C., from
440.degree. C. to 560.degree. C., from 450.degree. C. to
560.degree. C., from 455.degree. C. to 560.degree. C., from
460.degree. C. to 560.degree. C., from 465.degree. C. to
560.degree. C., from 470.degree. C. to 560.degree. C., from
475.degree. C. to 560.degree. C., from 480.degree. C. to
560.degree. C., from 485.degree. C. to 560.degree. C., from
490.degree. C. to 560.degree. C., from 495.degree. C. to
560.degree. C., from 495.degree. C. to 525.degree. C., from
500.degree. C. to 560.degree. C., from 505.degree. C. to
560.degree. C., from 510.degree. C. to 560.degree. C., from
515.degree. C. to 560.degree. C., from 520.degree. C. to
560.degree. C., from 525.degree. C. to 560.degree. C., from
530.degree. C. to 560.degree. C., from 535.degree. C. to
560.degree. C., from 540.degree. C. to 560.degree. C., from
260.degree. C. to 555.degree. C., from 260.degree. C. to
550.degree. C., from 260.degree. C. to 545.degree. C., from
260.degree. C. to 540.degree. C., from 260.degree. C. to
535.degree. C., from 260.degree. C. to 530.degree. C., from
260.degree. C. to 525.degree. C., from 260.degree. C. to
520.degree. C., from 260.degree. C. to 515.degree. C., from
260.degree. C. to 510.degree. C., from 260.degree. C. to
505.degree. C., from 260.degree. C. to 500.degree. C., from
260.degree. C. to 495.degree. C., from 260.degree. C. to
490.degree. C., from 260.degree. C. to 485.degree. C., from
260.degree. C. to 480.degree. C., from 260.degree. C. to
475.degree. C., from 260.degree. C. to 470.degree. C., from
495.degree. C. to 465.degree. C., from 260.degree. C. to
460.degree. C., from 260.degree. C. to 455.degree. C., from
260.degree. C. to 450.degree. C., from 260.degree. C. to
445.degree. C., from 260.degree. C. to 440.degree. C., from
260.degree. C. to 435.degree. C., from 260.degree. C. to
430.degree. C., from 260.degree. C. to 425.degree. C., from
260.degree. C. to 420.degree. C., from 260.degree. C. to
415.degree. C., from 260.degree. C. to 410.degree. C., from
260.degree. C. to 405.degree. C., from 260.degree. C. to
400.degree. C., from 260.degree. C. to 395.degree. C., from
260.degree. C. to 390.degree. C., from 260.degree. C. to
385.degree. C., from 260.degree. C. to 380.degree. C., from
260.degree. C. to 375.degree. C., from 260.degree. C. to
370.degree. C., from 495.degree. C. to 365.degree. C., from
260.degree. C. to 360.degree. C., from 260.degree. C. to
355.degree. C., from 260.degree. C. to 350.degree. C., from
260.degree. C. to 345.degree. C., from 260.degree. C. to
340.degree. C., from 260.degree. C. to 335.degree. C., from
260.degree. C. to 330.degree. C., from 260.degree. C. to
325.degree. C., from 260.degree. C. to 320.degree. C., from
260.degree. C. to 315.degree. C., from 260.degree. C. to
310.degree. C., from 260.degree. C. to 305.degree. C., from
260.degree. C. to 300.degree. C., from 260.degree. C. to
295.degree. C., from 260.degree. C. to 290.degree. C., from
260.degree. C. to 285.degree. C., from 260.degree. C. to
280.degree. C., from 260.degree. C. to 275.degree. C., or even from
260.degree. C. to 270.degree. C.
In the same or other embodiments, the catalytic reforming unit may
be operated at a pressure from 5 kg/cm.sup.2 to 25 kg/cm.sup.2,
from 5 kg/cm.sup.2 to 20 kg/cm.sup.2, from 5 kg/cm.sup.2 to 15
kg/cm.sup.2, from 5 kg/cm.sup.2 to 10 kg/cm.sup.2, from 10
kg/cm.sup.2 to 25 kg/cm.sup.2, from 15 kg/cm.sup.2 to 25
kg/cm.sup.2, or even from 20 kg/cm.sup.2 to 25 kg/cm.sup.2. In the
same or other embodiments, the catalytic reforming unit may be
operated at a pressure from 0.1 MPa to 5 MPa, from 0.1 MPa to 4
MPa, from 0.1 MPa to 3 MPa, from 0.1 MPa to 2 MPa, from 0.5 MPa to
5 MPa, from 1 MPa to 5 MPa, from 2 MPa to 5 MPa, from 3 MPa to 5
MPa, or even from 4 MPa to 5 MPa.
In the same or other embodiments, the hydrogen-to-oil ratio within
the catalytic reforming unit, on a volume basis, may be from 100 to
2500, from 100 to 2250, from 100 to 2000, from 100 to 1750, from
100 to 1500, from 100 to 1250, from 100 to 1000, from 100 to 750,
from 100 to 500, from 250 to 2500, from 500 to 2500, from 750 to
2500, from 1000 to 2500, from 1250 to 2500, from 1500 to 2500, from
1750 to 2500, from 2000 to 2500, or even from 2250 to 2500.
In the same or other embodiments, the catalytic reforming unit may
be operated with a LHSV from 0.5 h.sup.-1 to 40 h.sup.-1, from 0.5
h.sup.-1 to 35 h.sup.-1, from 0.5 h.sup.-1 to 30 h.sup.-1, from 0.5
h.sup.-1 to 25 h.sup.-1, from 0.5 h.sup.-1 to 20 h.sup.-1, from 0.5
h.sup.-1 to 15 h.sup.-1, from 0.5 h.sup.-1 to 10 h.sup.-1, from 0.5
h.sup.-1 to 5 h.sup.-1, from 0.5 h.sup.-1 to 4 h.sup.-1, from 1
h.sup.-1 to 40 h.sup.-1, from 4 h.sup.-1 to 40 h.sup.-1, from 5
h.sup.-1 to 40 h.sup.-1, from 10 h.sup.-1 to 40 h.sup.-1, from 15
h.sup.-1 to 40 h.sup.-1, from 20 h.sup.-1 to 40 h.sup.-1, from 25
h.sup.-1 to 40 h.sup.-1, from 30 h.sup.-1 to 40 h.sup.-1, or even
from 35 h.sup.-1 to 40 h.sup.-1.
In embodiments, the aromatic recovery complex performs a xylene
isomerization function and a xylene adsorption function. In
embodiments, the aromatic recovery complex, during the xylene
isomerization function, may be operated at a temperature from
250.degree. C. to 550.degree. C., from 270.degree. C. to
550.degree. C., from 280.degree. C. to 550.degree. C., from
290.degree. C. to 550.degree. C., from 300.degree. C. to
550.degree. C., from 300.degree. C. to 500.degree. C., from
310.degree. C. to 550.degree. C., from 320.degree. C. to
550.degree. C., from 330.degree. C. to 550.degree. C., from
340.degree. C. to 550.degree. C., from 350.degree. C. to
550.degree. C., from 360.degree. C. to 550.degree. C., from
370.degree. C. to 550.degree. C., from 370.degree. C. to
440.degree. C., from 380.degree. C. to 550.degree. C., from
390.degree. C. to 550.degree. C., from 400.degree. C. to
550.degree. C., from 410.degree. C. to 550.degree. C., from
420.degree. C. to 550.degree. C., from 430.degree. C. to
550.degree. C., from 440.degree. C. to 550.degree. C., from
450.degree. C. to 550.degree. C., from 455.degree. C. to
550.degree. C., from 460.degree. C. to 550.degree. C., from
465.degree. C. to 550.degree. C., from 470.degree. C. to
550.degree. C., from 475.degree. C. to 550.degree. C., from
480.degree. C. to 550.degree. C., from 485.degree. C. to
550.degree. C., from 490.degree. C. to 550.degree. C., from
495.degree. C. to 550.degree. C., from 500.degree. C. to
550.degree. C., from 505.degree. C. to 550.degree. C., from
510.degree. C. to 550.degree. C., from 515.degree. C. to
550.degree. C., from 520.degree. C. to 550.degree. C., from
525.degree. C. to 550.degree. C., from 530.degree. C. to
550.degree. C., from 535.degree. C. to 550.degree. C., from
540.degree. C. to 550.degree. C., from 250.degree. C. to
550.degree. C., from 250.degree. C. to 545.degree. C., from
250.degree. C. to 540.degree. C., from 250.degree. C. to
535.degree. C., from 250.degree. C. to 530.degree. C., from
250.degree. C. to 525.degree. C., from 250.degree. C. to
520.degree. C., from 250.degree. C. to 515.degree. C., from
250.degree. C. to 510.degree. C., from 250.degree. C. to
505.degree. C., from 250.degree. C. to 500.degree. C., from
250.degree. C. to 495.degree. C., from 250.degree. C. to
490.degree. C., from 250.degree. C. to 485.degree. C., from
250.degree. C. to 480.degree. C., from 250.degree. C. to
475.degree. C., from 250.degree. C. to 470.degree. C., from
495.degree. C. to 465.degree. C., from 250.degree. C. to
460.degree. C., from 250.degree. C. to 455.degree. C., from
250.degree. C. to 450.degree. C., from 250.degree. C. to
445.degree. C., from 250.degree. C. to 440.degree. C., from
250.degree. C. to 435.degree. C., from 250.degree. C. to
430.degree. C., from 250.degree. C. to 425.degree. C., from
250.degree. C. to 420.degree. C., from 250.degree. C. to
415.degree. C., from 250.degree. C. to 410.degree. C., from
250.degree. C. to 405.degree. C., from 250.degree. C. to
400.degree. C., from 250.degree. C. to 395.degree. C., from
250.degree. C. to 390.degree. C., from 250.degree. C. to
385.degree. C., from 250.degree. C. to 380.degree. C., from
250.degree. C. to 375.degree. C., from 250.degree. C. to
370.degree. C., from 495.degree. C. to 365.degree. C., from
250.degree. C. to 360.degree. C., from 250.degree. C. to
355.degree. C., from 250.degree. C. to 350.degree. C., from
250.degree. C. to 345.degree. C., from 250.degree. C. to
340.degree. C., from 250.degree. C. to 335.degree. C., from
250.degree. C. to 330.degree. C., from 250.degree. C. to
325.degree. C., from 250.degree. C. to 320.degree. C., from
250.degree. C. to 315.degree. C., from 250.degree. C. to
310.degree. C., from 250.degree. C. to 305.degree. C., from
250.degree. C. to 300.degree. C., from 250.degree. C. to
295.degree. C., from 250.degree. C. to 290.degree. C., from
250.degree. C. to 285.degree. C., from 250.degree. C. to
280.degree. C., from 250.degree. C. to 275.degree. C., from
250.degree. C. to 270.degree. C., from 250.degree. C. to
265.degree. C., or even from 250.degree. C. to 260.degree. C.
In the same or other embodiments, the aromatic recovery complex,
during the xylene isomerization function, may be operated at a
pressure from 1 MPa to 3 MPa, from 1 MPa to 2 MPa, from 1 MPa to
1.5 MPa, from 1 MPa to 1.2 MPa, from 1.2 MPa to 3 MPa, from 1.5 MPa
to 3 MPa, from 2 MPa to 3 MPa, or even from 2.5 MPa to 3 MPa.
In the same or other embodiments, the hydrogen-to-oil ratio within
the aromatic recovery complex during the xylene isomerization
function, on a molar basis, may be from 1 to 5, from 1 to 4, from 1
to 3, from 1 to 2, or even 1:1.
In the same or other embodiments, the aromatic recovery complex,
during the xylene isomerization function, may be operated with a
LHSV from 8 h.sup.-1 to 30 h.sup.-1, from 8 h.sup.-1 to 25
h.sup.-1, from 8 h.sup.-1 to 20 h.sup.-1, from 8 h.sup.-1 to 15
h.sup.-1, from 8 h.sup.-1 to 10 h.sup.-1, from 10 h.sup.-1 to 30
h.sup.-1, from 10 h.sup.-1 to 20 h.sup.-1, from 11 h.sup.-1 to 30
h.sup.-1, from 12 h.sup.-1 to 30 h.sup.-1, from 13 h.sup.-1 to 30
h.sup.-1, from 14 h.sup.-1 to 30 h.sup.-1, from 15 h.sup.-1 to 30
h.sup.-1, from 16 h.sup.-1 to 30 h.sup.-1, from 17 h.sup.-1 to 30
h.sup.-1, from 18 h.sup.-1 to 30 h.sup.-1, from 19 h.sup.-1 to 30
h.sup.-1, or even from 20 h.sup.-1 to 30 h.sup.-1.
In embodiments, the aromatic recovery complex, during the xylene
adsorption function, may be operated at a temperature from
80.degree. C. to 250.degree. C., from 85.degree. C. to 250.degree.
C., from 90.degree. C. to 95.degree. C., from 100.degree. C. to
250.degree. C., from 100.degree. C. to 225.degree. C., from
105.degree. C. to 250.degree. C., from 110.degree. C. to
500.degree. C., from 115.degree. C. to 250.degree. C., from
120.degree. C. to 250.degree. C., from 125.degree. C. to
250.degree. C., from 130.degree. C. to 250.degree. C., from
135.degree. C. to 250.degree. C., from 140.degree. C. to
250.degree. C., from 145.degree. C. to 250.degree. C., from
150.degree. C. to 440.degree. C., from 150.degree. C. to
200.degree. C., from 155.degree. C. to 250.degree. C., from
160.degree. C. to 250.degree. C., from 170.degree. C. to
250.degree. C., from 175.degree. C. to 250.degree. C., from
180.degree. C. to 250.degree. C., from 185.degree. C. to
250.degree. C., from 190.degree. C. to 250.degree. C., from
195.degree. C. to 250.degree. C., from 200.degree. C. to
250.degree. C., from 205.degree. C. to 250.degree. C., from
210.degree. C. to 250.degree. C., from 215.degree. C. to
250.degree. C., from 220.degree. C. to 250.degree. C., from
225.degree. C. to 250.degree. C., from 230.degree. C. to
250.degree. C., from 235.degree. C. to 250.degree. C., from
240.degree. C. to 250.degree. C., from 80.degree. C. to 245.degree.
C., from 80.degree. C. to 240.degree. C., from 80.degree. C. to
235.degree. C., from 80.degree. C. to 230.degree. C., from
80.degree. C. to 225.degree. C., from 80.degree. C. to 220.degree.
C., from 80.degree. C. to 215.degree. C., from 80.degree. C. to
210.degree. C., from 80.degree. C. to 205.degree. C., from
80.degree. C. to 200.degree. C., from 80.degree. C. to 195.degree.
C., from 80.degree. C. to 190.degree. C., from 80.degree. C. to
185.degree. C., from 80.degree. C. to 180.degree. C., from
80.degree. C. to 175.degree. C., from 80.degree. C. to 170.degree.
C., from 495.degree. C. to 165.degree. C., from 80.degree. C. to
160.degree. C., from 80.degree. C. to 155.degree. C., from
80.degree. C. to 150.degree. C., from 80.degree. C. to 445.degree.
C., from 80.degree. C. to 140.degree. C., from 80.degree. C. to
135.degree. C., from 80.degree. C. to 130.degree. C., from
80.degree. C. to 125.degree. C., from 80.degree. C. to 120.degree.
C., from 80.degree. C. to 115.degree. C., from 80.degree. C. to
110.degree. C., from 80.degree. C. to 105.degree. C., from
80.degree. C. to 100.degree. C., from 80.degree. C. to 95.degree.
C., or even from 80.degree. C. to 90.degree. C.
In the same or other embodiments, the aromatic recovery complex,
during the xylene adsorption function, may be operated at a
pressure from 0.1 MPa to 2 MPa, from 0.1 MPa to 1.9 MPa, from 0.1
MPa to 1.8 MPa, from 0.1 MPa to 1.7 MPa, from 0.1 MPa to 1.6 MPa,
from 0.1 MPa to 1.5 MPa, from 0.1 MPa to 1.4 MPa, 0.1 MPa to 1.3
MPa, from 0.1 MPa to 1.2 MPa, from 0.1 MPa to 1.1 MPa, from 0.1 MPa
to 1 MPa, from 0.1 MPa to 0.9 MPa, from 0.1 MPa to 0.8 MPa, from
0.1 MPa to 0.7 MPa, from 0.1 MPa to 0.6 MPa, from 0.1 MPa to 0.5
MPa, from 0.1 MPa to 0.4 MPa, from 0.1 MPa to 0.3 MPa, from 0.1 MPa
to 0.2 MPa, 0.2 MPa to 2 MPa, from 0.3 MPa to 2 MPa, from 0.4 MPa
to 2 MPa, from 0.5 MPa to 2 MPa, from 0.6 MPa to 2 MPa, from 0.7
MPa to 2 MPa, from 0.8 MPa to 2 MPa, 0.9 MPa to 2 MPa, from 1 MPa
to 2 MPa, from 1.1 MPa to 2 MPa, from 1.2 MPa to 2 MPa, from 1.3
MPa to 2 MPa, from 1.4 MPa to 2 MPa, from 1.5 MPa to 2 MPa, from
1.6 MPa to 2 MPa, from 1.7 MPa to 2 MPa, from 1.8 MPa to 2 MPa, or
even from 1.9 MPa to 2 MPa.
In the same or other embodiments, the aromatic recovery complex,
during the xylene adsorption function, may be operated with a LHSV
from 0.1 h.sup.-1 to 2 h.sup.-1, from 0.1 h.sup.-1 to 1.5 h.sup.-1,
from 0.1 h.sup.-1 to 1 h.sup.-1, from 0.1 h.sup.-1 to 0.5 h.sup.-1,
from 0.5 h.sup.-1 to 2 h.sup.-1, from 1 h.sup.-1 to 2 h.sup.-1, or
even from 1.5 h.sup.-1 to 2 h.sup.-1.
The adsorption zone(s) used in the process and apparatus described
herein is, in certain embodiments, at least two packed bed columns
which are gravity fed or pressure force-fed sequentially in order
to permit continuous operation when one bed is being regenerated,
i.e., swing mode operation. The columns contain an effective
quantity of adsorbent material, such as attapulgus clay, alumina,
silica gel silica-alumina, titania, fresh or spent catalysts, or
activated carbon. The packing can be in the form of pellets,
spheres, extrudates, natural shapes, or any combination thereof,
having an average size of 4 mesh to 60 mesh, and in certain
embodiments 4 mesh to 20 mesh, based on United States Standard
Sieve Series.
The packed columns are generally operated at a pressure in the
range of from 1 kg/cm.sup.2 to 30 kg/cm.sup.2, in certain
embodiments 1 kg/cm.sup.2 to 20 kg/cm.sup.2, and in further
embodiments 1 kg/cm.sup.2 to 10 kg/cm.sup.2, a temperature in the
range of from 20.degree. C. to 250.degree. C., in certain
embodiments 20.degree. C. to 150.degree. C., and in further
embodiments 20.degree. C. to 100.degree. C.; and a liquid hourly
space velocity of 0.1 h.sup.-1 to 10 h.sup.-1, in certain
embodiments 0.25 h.sup.-1 to 5 h.sup.-1, and in further embodiments
0.5 h.sup.-1 to about 2 h.sup.-1. The aromatic bottoms stream may
have an overall Hildebrand solubility parameter from 19 to 22. For
instance the aromatic bottoms stream may have a Hildebrand
solubility factor of 19, 20, 21, 22, or any fractional part
thereof, or the Hildebrand solubility factor may be from 19 to 21,
from 19 to 20, from 20 to 22, from 20 to 21, or even from 21 to
22.
Advantageously, the processes and systems described herein allow
for the reduction of the concentrations of nitrogen-containing
compounds, sulfur-containing compounds, and PNA compounds in a
heavy feedstream to a hydrocracking unit such as a DMO or DAO
feedstream by adsorbing the undesirable compounds on an adsorbent.
Saturated adsorbent can then be recycled by desorbing the unwanted
compounds using an aromatic bottoms stream from an aromatic
recovery complex. In addition, in recycle hydrocracking operations,
the concentration of PNA compounds that are formed in the
unconverted fractionator bottoms is reduced. Accordingly, the
overall efficiency of operation of the hydrocracking unit is
improved along with the effluent product quality.
According to an aspect, either alone or in combination with any
other aspect, a process for treating a hydrocarbon feedstream, the
hydrocarbon feedstream comprising nitrogen-containing compounds and
polynuclear aromatic compounds, includes: (i) contacting the
hydrocarbon feedstream with an adsorbent material to produce an
adsorbent having an increased content of nitrogen-containing
compounds and polynuclear compounds and an adsorbent-treated
hydrocarbon feedstream having a decreased content of
nitrogen-containing compounds and polynuclear aromatic compounds;
(ii) introducing the adsorbent-treated hydrocarbon feedstream to a
hydrocracking reaction unit to produce a hydrocracked effluent
stream; (iii) introducing a naphtha stream to a catalytic reforming
unit to produce a reformate stream; (iv) introducing the reformate
stream to an aromatic recovery complex to produce a light reformate
stream, a benzene-toluene-xylene (BTX) stream, and an aromatic
bottoms stream; and (v) introducing the aromatic bottoms stream to
the adsorbent having an increased content of nitrogen-containing
compounds and polynuclear compounds to produce an adsorbent having
a decreased content of nitrogen-containing compounds and
polynuclear compounds and an aromatic bottoms stream having an
increased content of nitrogen-containing compounds and polynuclear
aromatic compounds.
According to a second aspect, either alone or in combination with
any other aspect, the reformate stream comprises aromatics, alkyl
aromatics, naphthenes, olefins, and iso-paraffins.
According to a third aspect, either alone or in combination with
any other aspect, the aromatics bottoms stream has a Hildebrand
solubility factor of at least 19 MPa.sup.1/2.
According to a fourth aspect, either alone or in combination with
any other aspect, the adsorbent material is selected from the group
consisting of attapulgus clay, alumina, silica, titania, activated
carbon, fresh solid catalyst, spent solid catalyst, and a
combination of two or more thereof.
According to a fifth aspect, either alone or in combination with
any other aspect, the hydrocarbon feedstream is selected from the
group consisting of vacuum gas oil, de-metalized oil, de-asphalted
oil, coker gas oil, cycle oils, visbroken oil, coal liquids,
bio-oils, and a combination of two or more thereof.
According to a sixth aspect, either alone or in combination with
any other aspect, the aromatic bottoms stream comprises at least
one compound selected from the group consisting of alkylated
mono-aromatics, uncondensed bridged di-aromatics, condensed
di-aromatics, alkylated mono-aromatics, and mixtures of two or more
thereof.
According to a seventh aspect, either alone or in combination with
any other aspect, the process further includes conveying the
aromatic bottoms stream having an increased content of
nitrogen-containing compounds and polynuclear aromatic compounds to
a fuel oil pool or other process units to recover the aromatic
bottoms stream and the nitrogen-containing compounds and
polynuclear aromatic compounds.
According to an eighth aspect, either alone or in combination with
any other aspect, the polynuclear aromatic compounds comprise heavy
polynuclear aromatic compounds having seven or more fused aromatic
rings.
According to a ninth aspect, either alone or in combination with
any other aspect, the hydrocracking reaction unit performs
single-stage once through hydrocracking, series flow hydrocracking
with recycle, series flow hydrocracking without recycle, or two
stage recycle hydrocracking to produce the hydrocracked effluent
stream.
According to a tenth aspect, either alone or in combination with
any other aspect, the adsorbent material is in the form of pellets,
spheres, extrudates, or natural shapes and has a size in the range
of 4-60 mesh.
According to an eleventh aspect, either alone or in combination
with any other aspect, the process does not comprise a solvent
desorption step to produce an adsorbent having a decreased content
of nitrogen-containing compounds and polynuclear compounds and an
aromatic bottoms stream having an increased content of
nitrogen-containing compounds and polynuclear aromatic
compounds.
According to a twelfth aspect, either alone or in combination with
any other aspect, the process further includes introducing the
hydrocracked effluent stream to a high pressure separation zone to
produce a degassed effluent stream; introducing the degassed
effluent stream to a fractionating zone to produce at least one
hydrocarbon fraction comprising nitrogen-containing compounds and
polynuclear compounds; and contacting the at least one hydrocarbon
fraction comprising nitrogen-containing compounds and polynuclear
compounds with an adsorbent material to produce an adsorbent having
an increased content of nitrogen-containing compounds and
polynuclear compounds and a second adsorbent-treated hydrocarbon
feedstream having a decreased content of nitrogen-containing
compounds and polynuclear aromatic compounds.
According to a thirteenth aspect, either alone or in combination
with any other aspect, a system for treating a hydrocarbon
feedstream, the hydrocarbon feedstream comprising
nitrogen-containing compounds and polynuclear aromatic compounds,
including: an adsorption zone comprising an adsorbent material for
adsorbing at least a portion of the nitrogen-containing compounds
and polynuclear aromatic compounds thereby converting the
hydrocarbon feedstream into an adsorbent-treated hydrocarbon
feedstream having a decreased content of nitrogen-containing
compounds and polynuclear aromatic compounds; an aromatic recovery
complex for producing an aromatic bottoms stream, the aromatic
recovery complex having an outlet that is fluidly coupled to an
inlet of the adsorption zone; and a conduit in fluid communication
with the outlet of the aromatic recovery complex and the inlet of
the adsorption zone for conveying at least a portion of the
aromatic bottoms stream to the adsorption zone for desorbing the
nitrogen-containing compounds and polynuclear aromatic compounds
from the adsorbent materials.
According to a fourteenth aspect, either alone or in combination
with any other aspect, the aromatics bottoms stream has a
Hildebrand solubility factor greater than 19.
According to a fifteenth aspect, either alone or in combination
with any other aspect, the aromatics bottoms stream has a
Hildebrand solubility factor from 19 to 22.
According to a sixteenth aspect, either alone or in combination
with any other aspect, the adsorbent material is selected from the
group consisting of attapulgus clay, alumina, silica, titania,
activated carbon, fresh solid catalyst, spent solid catalyst, and a
combination of two or more thereof.
According to a seventeenth aspect, either alone or in combination
with any other aspect, the hydrocarbon feedstream is selected from
the group consisting of vacuum gas oil, de-metalized oil,
de-asphalted oil, coker gas oil, cycle oils, visbroken oil, coal
liquids, bio-oils, and a combination of two or more thereof.
According to an eighteenth aspect, either alone or in combination
with any other aspect, the aromatic bottoms stream comprises at
least one compound selected from the group consisting of alkylated
mono-aromatics, uncondensed bridged di-aromatics, condensed
di-aromatics, alkylated mono-aromatics, and mixtures of two or more
thereof.
According to a nineteenth aspect, either alone or in combination
with any other aspect, the polynuclear aromatic compounds comprise
heavy polynuclear aromatic compounds having seven or more fused
aromatic rings.
According to a twentieth aspect, either alone or in combination
with any other aspect, the adsorbent material is in the form of
pellets, spheres, extrudates, or natural shapes and has a size in
the range of 4-60 mesh.
Example
Using embodiments described above, an exemplary hydrocracking pilot
plant test was conducted, as follows. The following examples are
merely illustrative and should not be interpreted as limiting the
scope of the present disclosure.
50 grams of a hydrocracking unit recycle stream containing 4006 ppm
by weight HPNA was treated in an adsorption column containing 5.03
g of Attapulgus clay. After collecting the treated material, the
column was washed with 50 grams pentane to elute PNA hydrocarbons
from the adsorption column, followed by 50 grams of aromatic
bottoms stream to elute the HPNA, and then by 50 grams of
tetrahydrofuran to elute residual aromatic bottoms. The material
balance and HPNA content of the stream is shown in Table 2. As
seen, the aromatic bottoms stream was able to desorb the majority
of the HPNA from the adsorbents.
TABLE-US-00003 TABLE 2 Material balance and HPNA content of the
feedstream and stream out In-Out Component g HPNA (ppmw) HPNA (g)
In Feedstream 50.0 4006 0.2003 In Total In 50.0 4006 0.2003 Out
Treated feedstream 48.2 3747 0.1808 Out Aromatic Bottoms 47.6 265.4
0.0126 Out Tetrahydrofuran fraction 8.4 40.5 0.0020 Out Total Out
0.1954
It is noted that recitations in the present disclosure of a
component of the present disclosure being "operable" or
"sufficient" in a particular way, to embody a particular property,
or to function in a particular manner, are structural recitations,
as opposed to recitations of intended use. More specifically, the
references in the present disclosure to the manner in which a
component is "operable" or "sufficient" denotes an existing
physical condition of the component and, as such, is to be taken as
a definite recitation of the structural characteristics of the
component.
Having described the subject matter of the present disclosure in
detail and by reference to specific embodiments, it is noted that
the various details disclosed in the present disclosure should not
be taken to imply that these details relate to elements that are
essential components of the various embodiments described in the
present disclosure. Further, it will be apparent that modifications
and variations are possible without departing from the scope of the
present disclosure, including, but not limited to, embodiments
defined in the appended claims.
The singular forms "a", "an" and "the" include plural referents,
unless the context clearly dictates otherwise.
Throughout this disclosure ranges are provided. It is envisioned
that each discrete value encompassed by the ranges are also
included. Additionally, the ranges which may be formed by each
discrete value encompassed by the explicitly disclosed ranges are
equally envisioned.
As used in this disclosure and in the appended claims, the words
"comprise," "has," and "include" and all grammatical variations
thereof are each intended to have an open, non-limiting meaning
that does not exclude additional elements or steps.
As used in this disclosure, terms such as "first" and "second" are
arbitrarily assigned and are merely intended to differentiate
between two or more instances or components. It is to be understood
that the words "first" and "second" serve no other purpose and are
not part of the name or description of the component, nor do they
necessarily define a relative location, position, or order of the
component. Furthermore, it is to be understood that the mere use of
the term "first" and "second" does not require that there be any
"third" component, although that possibility is contemplated under
the scope of the present disclosure.
* * * * *